1. Technical Field
The present invention relates generally to phase detectors and, more particularly, to a phase detector for a power delivery system which determines the phase of a reflection coefficient using two time varying signals of equal fundamental frequency.
2. Discussion
In a typical radio frequency (RF) plasma generator arrangement, a high power RF source produces an RF signal at a predetermined frequency, such as 2 MegaHertz (MHz), 4 MHz, or 13.56 MHz. The RF signal is output on a transmission line to a plasma chamber. Because an impedance mismatch often exists between the RF power source and the plasma chamber, a matching network is inserted between the RF power source and the plasma chamber. The plasma chamber often introduces non-linearities, which result in losses in the transmission line and in the impedance network, so that less than a full output power of the RF power source is applied to the plasma chamber.
In order to quantify this mismatch, conventional systems introduce a probe at the input to the plasma chamber to detect the voltage and current of the radio frequency signal as it is applied to the plasma chamber. Accurately measuring the voltage and current in close proximity to the plasma chamber provides a better indication of the quality of the plasma. A better indication of the quality of the plasma in turn enables better control of the etching or deposition process taking place within the plasma chamber. Conventional probes are limited in that they monitor the voltage, current, and phase angle of the signal applied to the plasma chamber.
Another type of sensor placed in proximity to the plasma chamber provides only magnitude information of the power applied to the plasma chamber, the forward power, and power reflected back from the plasma chamber, the reflected power. While the forward and reverse power is extremely useful in controlling the RF power supply in order to deliver the optimal RF signal to the plasma chamber, conventional sensors which measure the forward and reverse power do not presently provide phase information. As is known to those skilled in the art, phase information enables a determination of the reflection coefficient. Conventional power sensors are directional pickups and do not enable the determination of the relative phase between the forward and reverse power.
Thus, it is desirable to provide a phase detector for use in conjunction with a directional pickup which provides both forward power, reverse power, and phase information.
The present invention is directed to an apparatus including a power delivery system coupler receiving an output from a power generator. The coupler detects a first parameter and a second parameter, the coupler generates a respective first signal and a second signal. Each signal varies in accordance with the respective first and second parameters. A phase detector receives the first signal and the second signal from the coupler. The phase detector determines a relative phase between the first signal and the second signal in accordance with the first parameter and the second parameter.
For a more complete understanding of the invention, its objects and advantages, reference should be made to the following specification and to the accompanying drawings.